Tag: Chambers of heart

Chambers of heart

Chambers of heart


CHAMBERS OF HEART    
  • The human heart has four chambers: two upper chambers (the atria) and two lower ones (the ventricles)

RIGHT ATRIUM:

  • Has thinnest walls of the four chambers.
  • Forms rt. border of heart.
  • It is divided by (crista terminalis) into two parts:-

1. Rough anterior part or atrium proper (pectinate part), including auricle

  • It is derived from right half of primitive atrial chamber.
  • There is a series of transverse muscular ridges calles musculi pectinate which are attached to crista terminalis & gives appearance like“teeth of a comb”.
  • SA node is situated in the upper part of crista terminalis.
  • Auricle lies in the superomedial portion.

2. Posterior smooth part or sinus venorum

  • It is derived from absorption of right horn of sinus venosus.
  • It has openings of:

    i. Superior vena cava- Has no valve.

    ii. Inferior vena cava- 

  • Orifice is guarded by a rudimentary valve of IVC (Eustachian valve) derived from embryonic right venous valve, which directs the blood fromIVC (Eustachian valve) derived from embryonic right venous valve, which directs the blood from IVC towards foramen ovalve in fetal live.
  • This valve is nonfunctional in adults.

    iii. Coronary sinus-

  • Orifice lies b/w tricuspid orifice & IVC orifice .
  • It is guarded by a functional semilunar valve (thebesian valve)

    iv. Venae cardis minimae (thebesian veins)- Open through foramina venorum minimarum

    v. Anterior cardiac vein

    vi. Right marginal vein- open into coronary sinus (not in right atrium)

→ Crista terminalis (divides the right atrium into anterior & posterior part) is a ridge of smooth muscle fibers extending from the SVC to valve of IVC.

→ It is developed from developed from embryonic right venous valve & is represented on the surface by sulcus terminalis.

INTERATRIAL SEPTAL REGION

  • Interatrial septum develops from approximation of embryonic  septum primum & septum secundum.
  • Features on right atrial side are:
  1.Fossa ovalis
  • Oval shaped depression lying above the level of IVC opening in the interatrial septum.
  • It is the embryological remnant of foramen ovale, which connects right atrium to left atrium in embryonic life.
  • Floor of the fossa ovalis is formed by septum primum.
  2. Limbus fossa ovalis (Annulus ovalis):
  • It is thickened rim present above the fossa ovalis.
  • It presents the lower free margin of septum secundum.
  3. Triangle of Koch
  • It is a triangular region in the lower part of interatrial septum which contains AV node.
  • It is bounded above by tendon of Todaro below by base of septal leaflet of tricuspid valve & anteriorly (base) by orifices of coronary sinus.
  • Immediately above the membranous septum, the septal region shows a slight bulge known as Torus aorticus.
  • Torus aorticus is an impression in the cavity of Right atrium.  
LEFT ATRIUM:
  • Has slightly thicker walls than right atrium.
  • Left atrium forms the base of the heart.
  • Left atrium forms the anterior wall of oblique sinus of pericardium. It lies in front of esophagus.
  • Divided into:
  1.  Posteriorly smooth walled part–  receiving 4 pulmonary veins which develops from absorption of embryonic pulmonary veins.
  2. Rough walled part (left auricle)- having network of musculi pectinati developing from left half of primitive atrium.
  • Left auricle projects anteriorly to overlap infundibulum of right ventricle.

RIGHT VENTRICLE:

  • It is anteroinferior chamber & projects ro the left of right atrium.
  • It is in contact with the sternum.
  • Anterior wall forms most of the sternocostal surface of the heart.
  • Divided into:

1. Rough inflowing part (ventricle proper)

  • It is developed from right half of primitive ventricle.
  • Its interior is rough due to the presence of muscular ridges known as trabeculae carnae, which are more prominent in apical region.
  • Trabeculae carneae are of 3 types:-

  i. Ridges- Linear elevations.

  • Supraventricular crest- a ridge present b/w the pulmonary & atrioventricular orifices, extends downwards in the posterior wall of infundibulum.

  ii. Bridges- Muscular elevations with fixed ends on ventricular walls, the center being free.

  • Septomarginal trabecula: It is specialised bridge which extends from the right ventricularsetum to the base of anterior paoillary muscle.

  iii. Papillary muscles- are conical projections of muscle fiber bundles.

  • There are three papillary muscles in the right & two in the left ventricle.
  • They regulate closure of atrioventricular valves.

2. Smooth outflowing part (infundibulum or conus arteriosus)

  • Develops from midportion of bulbus cordis.
  • Surrounds pulmonary valve Supraventricular crest (crista supraventricularis) or infundibuloventricular crest separates tricuspid (AV) orifice, i.e inlet & outlet parts.
  • Crista supraventricularis Separate Tricuspid valve & Pulmonary valve and Apex trabeculated both.

LEFT VENTRICLE:

  • It has three times thicker walls than right ventricle.
  • It is divided into two parts:

i. Rouh walled inflowing part (left ventricular proper) developing from left of primitive ventricle.

  • Trabeculae carnae (muscular bridges) are more prominent than that in right ventricle.

ii. Smooth walled outflowing part (aortic vestibule) developing from bulbus cordis.

  • Aortic vestibule leads to ascending aorta.
Interventricular septum
  • The membranous part of the interventricular septum is situated in between Left ventricle and right atrium.
  • Depolarisation of cardiac ventricular muscle starts from Left side of inter ventricular septum
Exam Question
 
  • SA node is situated in the upper part of crista terminalis.
  • Auricle lies in the superomedial portion.
  • Floor of the fossa ovalis is formed by septum primum..
  • Left atrium forms the base of the heart.
  • Left atrium forms the anterior wall of oblique sinus of pericardium. It lies in front of esophagus.
  • Left auricle projects anteriorly to overlap infundibulum of right ventricle.
  • The anterior surface, or sternocostal surface, is mostly made up of the right ventricle.
  • Torus aorticus is an impression in the cavity of Right atrium
  •  Superior vena cava- Has no valve.
Don’t Forget to Solve all the previous Year Question asked on Chambers of heart

Chambers of heart

CHAMBERS OF HEART

Q. 1

Which chamber’s anterior wall forms most of the sternocostal surface of the heart?

 A

Left atrium

 B

Left ventricle

 C

Right atrium

 D

Right ventricle

Q. 1

Which chamber’s anterior wall forms most of the sternocostal surface of the heart?

 A

Left atrium

 B

Left ventricle

 C

Right atrium

 D

Right ventricle

Ans. D

Explanation:

The heart has three important surfaces: an anterior surface, a diaphragmatic surface, and a pulmonary surface. The anterior surface, or sternocostal surface, is mostly made up of the right ventricle. The diaphragmatic surface is mostly the left ventricle, but a little bit of the right ventricle sits on the diaphragm as well. Finally, the pulmonary surface, which is on the left, is mostly made up of the left ventricle.


Q. 2

Torus aorticus is an impression in the cavity of?

 A

Right atrium

 B

Left atrium

 C

Right ventricle

 D

Left ventricle

Q. 2

Torus aorticus is an impression in the cavity of?

 A

Right atrium

 B

Left atrium

 C

Right ventricle

 D

Left ventricle

Ans. A

Explanation:

Torus aorticus is a bulge in the right atrial wall anterosuperiorly above the membranous septum. It is superior to the coronary sinus and anterior to the fossa ovalis. It represents the deeper and anterior surface of the posterior sinus and cusp of the aortic valve.


Q. 3

Which of the following cardiac chamber forms the base of the heart?

 A

Right atrium

 B

Right ventricle

 C

Left atrium

 D

Left ventricle

Q. 3

Which of the following cardiac chamber forms the base of the heart?

 A

Right atrium

 B

Right ventricle

 C

Left atrium

 D

Left ventricle

Ans. C

Explanation:

Posterior surface or base of the heart is entirely formed by the left atrium which receives the 4 pulmonary veins. 
  • The anterior or sternocostal surface consist of the right atrium, vertical atrioventricular groove, and the right ventricle with a narrow strip of left ventricle appearing on the horizon of the left border.
  • The inferior or diaphragmatic surface consist of the right atrium receiving the inferior vena cava, the anteroposterior atrioventricular groove and to the left this the ventricular surface is made up of one third right ventricle and two third left ventricle separated by posterior interventricular branch of right coronary artery.

Q. 4

The membranous part of the interventricular septum is situated in between:

 A

Right ventricle and right atrium

 B

Right ventricle and left atrium

 C

Left ventricle and left atrium

 D

Left ventricle and right atrium

Q. 4

The membranous part of the interventricular septum is situated in between:

 A

Right ventricle and right atrium

 B

Right ventricle and left atrium

 C

Left ventricle and left atrium

 D

Left ventricle and right atrium

Ans. D

Explanation:

Membranous part of ventricular system is a small portion of the ventricular and atrioventricular septum located at the base of the heart adjacent to the anteroseptal tricuspid commissure , the right aortic posterior valve commissure and the anterior mitral valve leaflet. Because of the apical displacement of the tricuspid valve compared to mitral valve, a portion of the membranous septum  separates the left ventricle from the right atrium.

 
The remaining three regions of the ventricular septum are inlet, outlet and trabecula. They are all muscular and and they radiate out from the membranous septum.
 

Q. 5

In humans, where does depolarisation of cardiac ventricular muscle starts from?

 A

Posterobasal part of ventricle

 B

Left side of inter ventricular septum

 C

Uppermost part of interventricular septum

 D

Basal portion of ventricle

Q. 5

In humans, where does depolarisation of cardiac ventricular muscle starts from?

 A

Posterobasal part of ventricle

 B

Left side of inter ventricular septum

 C

Uppermost part of interventricular septum

 D

Basal portion of ventricle

Ans. B

Explanation:

In humans, depolarization of the ventricular muscle starts at the left side of the interventricular septum and moves first to the right across the mid portion of the septum.
 
The wave of depolarization then spreads down the septum to the apex of the heart. It then returns along the ventricular walls to the AV groove, proceeding from the endocardial to the epicardial surface. The last parts of the heart to be depolarized are the posterobasal portion of the left ventricle, the pulmonary conus, and the uppermost portion of the septum.

Q. 6

True about anatomy of right ventricle:

 A

TV & PV Share fibrous continuity

 B

More prominent trabeculation

 C

Crista supraventricularis Separate Tricuspid valve & Pulmonary valve and Apex trabeculated both

 D

All

Q. 6

True about anatomy of right ventricle:

 A

TV & PV Share fibrous continuity

 B

More prominent trabeculation

 C

Crista supraventricularis Separate Tricuspid valve & Pulmonary valve and Apex trabeculated both

 D

All

Ans. D

Explanation:

All Correct

Right ventricle is situated anteriorlyQ. As the anterior (sternocostal) surface of heart consists mainly of right ventricleQ with right atrium on its right and a narrow strip of left ventricle left border. The tip of left auricular appendage peeps over the to of this border.


Q. 7

Base of heart is formed by

 A

Rt. ventricle

 B

LV

 C

LV + RV

 D

RA + LA

Q. 7

Base of heart is formed by

 A

Rt. ventricle

 B

LV

 C

LV + RV

 D

RA + LA

Ans. D

Explanation:

D i.e. RA + LA 

The base of heart forms its posterior surface. It is formed mainly by the left atriumQ and by small part of right atriumQ.


Q. 8

Base of the heart is formed mainly by:

 A

Right atrium

 B

Left atrium

 C

Right ventricle

 D

Left ventricle

Q. 8

Base of the heart is formed mainly by:

 A

Right atrium

 B

Left atrium

 C

Right ventricle

 D

Left ventricle

Ans. B

Explanation:

The heart has three surfaces: sternocostal (anterior), diaphragmatic (inferior), and a base (posterior).

It also has an apex, which is directed downward, forward, and to the left.

The sternocostal surface is formed mainly by the right atrium and the right ventricle.

The right border is formed by the right atrium; the left border, by the left ventricle and part of the left auricle.

The diaphragmatic surface of the heart is formed mainly by the right and left ventricles. The inferior surface of the right atrium, into which the inferior vena cava opens, also forms part of this surface.

The base of the heart, or the posterior surface, is formed mainly by the left atrium, into which open the four pulmonary veins.


Q. 9

In PA view of X-ray chest, right border of the heart is formed by all except:

 A

Superior venacava

 B

Inferior venacava

 C

Right atrium

 D

Left atrial appendage

Q. 9

In PA view of X-ray chest, right border of the heart is formed by all except:

 A

Superior venacava

 B

Inferior venacava

 C

Right atrium

 D

Left atrial appendage

Ans. D

Explanation:

Ans. Left atrial appendage


Q. 10

Right border of heart is formed by ‑

 A

Right ventricle

 B

Right atrium

 C

SVC

 D

IVC

Q. 10

Right border of heart is formed by ‑

 A

Right ventricle

 B

Right atrium

 C

SVC

 D

IVC

Ans. B

Explanation:

External features of heart

The heart has following borders and surfaces :- 

A) Borders

i) Right border :- Formed by right atrium.

ii)  Left border (obtuse margin):- Formed mainly by left ventricle and partly by left auricle (in its upper most part).

iii) Inferior border (acute margin):- Formed mainly by right ventricle and partly by left ventricle near apex.

iv) Upper border :- Mainly by left atrium and partly by right atrium where SVC enters.

v) Apex :- Formed by left ventricle.

B) Surfaces

i) Anterior (sternocostal) surface :- Formed mostly by right ventricle (major) and right auricle and partly by left ventricle and left auricle.

ii) Inferior (diaphragmatic) surface :- It is formed by left ventricle (left 2/3) and right ventricle (right 1/3). It is traversed by posterior interventricular groove (PIV) containing PIV branch of RCA.


Q. 11

Crista terminalis is present in ‑

 A

Left atrium

 B

Left ventricle

 C

Right atrium

 D

Right ventricle

Q. 11

Crista terminalis is present in ‑

 A

Left atrium

 B

Left ventricle

 C

Right atrium

 D

Right ventricle

Ans. C

Explanation:

Crista terminalis (divides the right atrium into anterior and posterior part) is a ridge of smooth muscle fibers extending from the SVC to valve of IVC.

It is developed from embryonic right venous valve and is represented on the surface by sulcus terminalis.


Q. 12

Where is torus aorticus located 

 A

Left atrium

 B

Right atrium

 C

Aorta

 D

Left ventricle

Q. 12

Where is torus aorticus located 

 A

Left atrium

 B

Right atrium

 C

Aorta

 D

Left ventricle

Ans. B

Explanation:

Torus aorticus is a buldge in the right atrial septum sited superiorly and anteriorly.

It is produced due to adjacent nonocoronary aortic sinus at the base of ascending aorta.

It is superior to coronary sinus and anterior to fossa ovalis.


Q. 13

Not true about superior vena cava 

 A

Opens into right ventricle

 B

Enters the heart at level of 3rd costal

 C

Pierces paricardium at 2nd costal cartilage

 D

Receives azygos vein behind sternal angle

Q. 13

Not true about superior vena cava 

 A

Opens into right ventricle

 B

Enters the heart at level of 3rd costal

 C

Pierces paricardium at 2nd costal cartilage

 D

Receives azygos vein behind sternal angle

Ans. A

Explanation:

SVC opens in to right atrium (not right ventricle).

Superior vena-cava

  • SVC collects blood from the upper half of the body and drains into the right atrium. It is formed by the union of two brachiocephalic veins at the level of lower border of 1″ right costal cartilage. It passes vertically downwards behind the right border of sternum and piercing the pericardium at the level of the second costal cartilage, enters the upper border of the right atrium to end in the upper and posterior part of sinus venorum at the lower border of third right costal cartilage (opposite Ts vertebra).
  • Behind the sternal angle (T4 vertebral level), SVC receives the azygos vein.
  • SVC is divided into two parts –

i) Upper half (extrapericardial) 

ii) Lower half (intrapericardial)


Q. 14

Not true about right atrium ‑

 A

Posterior part is smooth

 B

Anterior part is derived from absorption of right horn of sinus venosus

 C

Fossa oval i s repressent remnant of foramen ovale

 D

Anterior and posterior parts are divided by Crista terminalis

Q. 14

Not true about right atrium ‑

 A

Posterior part is smooth

 B

Anterior part is derived from absorption of right horn of sinus venosus

 C

Fossa oval i s repressent remnant of foramen ovale

 D

Anterior and posterior parts are divided by Crista terminalis

Ans. B

Explanation:

Ans. is ‘b’ i.e., Antirior part is derived from absorption of right horn of sinus venosus

Sinus venarum (posterior part of right atrium) is derived from absorption of right horn of sinus venosus (not anterirpart).

Right atrium

It has thinnest walls of the four chambers. It is divided by crista terminalis into two parts :-

i) Rough anterior part or atrium proper (pectinate part), including auricle.

It is derived from right half of primitive atrial chamber. There is a series of transverse muscular ridges called musculi pectinate which are attached to crista terminalis and gives appearance like “teeth of a comb”. SA node is situated in the upper part of crista terminates. Auricle lies in the superomedial portion.

ii) Posterior smooth part or sinus venorum.

It is derived from absorption of right horn of sinus venosus. It has openings of :‑

I) Superior vena cava :- Has no valve.

2)   Inferior vena cava :- Orifice is guarded by a rudimentary valve of IVC (Eustachian valve) derived from embryonic right venous valve, which directs the blood from IVC towards foramen ovale in fetal live. This valve is nonfunctional in adults.

3) Coronary sinus :- Orifice lies between tricuspid orifice and IVC orifice. It is guarded by a functional semilunar valve (thebesian valve). Thebesian valve develops from right venous valve.

4) Venae cardis minimae (thebesian veins):- Open through foramina venorum minimarum.

5) Anterior cardiac vein

6) Right marginal vein :- Sometimes it may open into coronary sinus (not in right atrium).

iii) Interatrial septal region

Interatrial septum develops from approximation of embryonic septum primum and septum secundum. Feauters on right atrial side are :

1) Fossa ovalis :- Oval shaped depression lying above the level of IVC opening in the interatrial septum. It is the embryologic remnant of foramen ovale, which connects right atrium to left atrium in embryonic life. Floor of the fossa ovalis is formed by septum primum.

2) Limbus fossa ovalis (Annulus ovalis) :- It is thickened rim present above the fossa ovalis. It represents the lower free margin of septum secundum.

3) Triangle of Koch :- It is a triangular region in the lower part of interatrial septum which contains AV node. It is bounded above by tendon of Todaro below by base of septal leaflet of tricuspid valve and anteriorly (base) by orifices of coronary sinus.

Immediately above the membranous septum, the septal region shows a slight bulge known as torus aorticus, produced by right posterior (non-coronary) aortic sinus (of valsalva).


Q. 15

Not true about the structure marked with red arrow:

 A

Opens into right ventricle

 B

Enters the heart at level of 3rdcostal

 C

Pierces paricardium at 2nd costal cartilage

 D

Receives azygos vein behind sternal angle

Q. 15

Not true about the structure marked with red arrow:

 A

Opens into right ventricle

 B

Enters the heart at level of 3rdcostal

 C

Pierces paricardium at 2nd costal cartilage

 D

Receives azygos vein behind sternal angle

Ans. A

Explanation:

 Ans;A).Opens into right ventricle

This structure is superior venacava

SVC opens in to right atrium (not right ventricle).

Superior vena-cava

  • SVC collects blood from the upper half of the body and drains into the right atrium. 
  • It is formed by the union of two brachiocephalic veins at the level of lower border of 1″ right costal cartilage. 
  • It passes vertically downwards behind the right border of sternum and piercing the pericardium at the level of the second costal cartilage, enters the upper border of the right atrium to end in the upper and posterior part of sinus venorum at the lower border of third right costal cartilage.

Structure and Course of superior vena cava

  • It is formed by the left and right brachiocephalic veins (also referred to as the innominate veins), which also receive blood from the upper limbs, eyes and neck, behind the lower border of the first right costal cartilage.
  • It passes vertically downwards behind first intercostal space and receives azygos vein just before it pierces the fibrous pericardium opposite right second costal cartilage and its lower part is intrapericardial.
  • And then, it ends in the upper and posterior part of the sinus venarum of the right atrium, at the upper right front portion of the heart.
  • No valve divides the superior vena cava from the right atrium. As a result, the (right) atrial and (right) ventricular contractions are conducted up into the internal jugular vein and, through the sternocleidomastoid muscle, can be seen as the jugular venous pressure.


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